I have been unsuccessful at getting the Twonky Server on my WDEx4 Cloud and my Imac to properly
play back video files to our Vizio E601i-A3 smart TV. The videos all playback fine on my Sony
Google TV. I can copy the videos directly off of my WDEx4 or my Imac to a USB pen, plug it
into the Vizio TV and the videos play just fine, so I do not think it is anything to do with the
format of the video itself, which is H.264 and AC3.

I looked and do not see Vizio in the list of devices in the drop down menu, so its generally
picked the generic media receiver. That said for some reason I see the TV sometimes twice
in the list of Media Receivers... Also the Vizio is Very Slow when moving through the
list of movies on my WD and Imac players, while the Sony is very quick and responsive through
the folder listing of movies.

Had the same with Vizio. After spending hours with Vizio support and Internet research:
you can't fix it. It's a known Vizio bug.
I plugged in a Roku Stick and everything run's fantastic. As a second TV we have a Loewe (German brand) and this is running with WD Mycloud and Twonky without any problem